This invention relates in general to internal combustion engines and more specifically to air intake heating systems for diesel engines which aid in cold weather starting and control white smoke exhaust omissions upon starting of the engine and as required thereafter during operation of the engine.
An undesirable phenomenon known as "white smoke" is a frequent side effect of no load or light load diesel engine operation at low temperatures. This phenomenon is essentially the result of unburned hydrocarbons in the engine exhaust and is attributable to misfiring or incomplete combustion in some or all cylinders. White smoke is both a respiratory and optical irritant as well as having an adverse affect upon visibility. While white smoke is not a regulated exhaust emission, sociability of the engine or vehicle suffers as a result of the production of white smoke.
In order to improve acceptance of small direct injection diesel engines used in marine applications, a means of cold starting and reducing white smoke is required during engine starting and thereafter during engine operation. The means for cold starting and reducing white smoke should be compatible with and make efficient use of the available power associated with a small direct injection diesel engine used in marine applications.
Various prior art devices have been employed to effect heat transfer to intake air of a diesel engine. A manifold heater system helps raise the temperature of the combustion air as intake manifold air passes through the intake manifold of the engine by means of an electrically heated element or a combustion burner using a liquid or gaseous fuel. One such electrical heating system is marketed by Robert Bosch, a German company, for use with direct injection engines of up to 2 liters displacement. See Diesel Engine Reference Book edited by L. R. C. Lilly, Butterworth and Company (Publishers) 1984.
An alternate device employed to improve cold starting characteristics of diesel engines is the glow plug device. A heating element or glow plug is located within each combustion chamber of the diesel engine. Each of the glow plugs is connected in parallel to the vehicle battery and power is supplied for 30 seconds or more to the glow plugs prior to starting the engine. The glow plug has the effect of heating the internal combustion area of the engine and improving starting performance when temperatures drop below the ambient temperature required for a diesel engine to ignite fuel. Glow plugs are manufactured by Robert Bosch in Germany, Delco Remy in the United States and the Lucas organization in Great Britain. Although an aid in cold starting, glow plugs do not reduce engine production of white smoke after starting.
U.S. Pat. No. 4,723,527 to Panten, et al. discloses an apparatus including a microprocessor controller for increasing inlet air temperature of an engine by way of exhaust gas recirculation techniques. Panten provides a postheat system for heating intake air after the vehicle engine is running. Pace, U.S. Pat. No. 4,367,700, discloses an electric resistance heating element for heating inlet air of an engine until a control unit senses a preset operating temperature of inlet air.
Pace does not address electrical power consumption limitations nor does Pace provide a systems approach for control of white smoke emissions. Dinger et al., U.S. Pat. No. 4,207,848, discloses a microprocessor controlled heat exchanger wherein heat from electrically heated water is transferred to intake air. The apparatus shown in U.S. Pat. No. 4,186,560 to Frankl includes a turbo-supercharger system which provides for diversion of compressed air through an air heater. The air heater in Frankl derives heat from the combustion of hydrocarbon fuels and transfers that heat to the compressed air flowing through the heat-exchanger. Kurihara et al., U.S. Pat. No. 4,681,070, discloses a suction gas heater control device for an engine which includes the capability to heat such gas for a predetermined period of time after the engine has been brought into stall after complete firing, thus facilitating engine restarting after stalling. Shea et al., U.S. Pat. No. 4,944,260, discloses an air intake heater system for internal combustion engines including a microprocessor controller, intake manifold air temperature sensing means, water in fuel sensors, and electrical air intake heating elements actuated by the microprocessor. Further air heating systems deriving heat from a running engine or combustible fuels to heat intake air are shown in patents to Kearsley et al., U.S. Pat. No. 4,545,357 (heating intake air), and Kawamura, U.S. Pat. No. 4,625,910 (heating air delivered into a passenger compartment).
An air intake heater system operational during both starting of an engine and as required thereafter during engine operation would enhance diesel engine applications. Such a system would provide effective cold start assistance as well as reduce white smoke pollutants from engine exhaust during both engine starting and running conditions.